Most commercially available MEMS microphones or silicon microphones are formed by two chips, an application specific integrated circuit (ASIC) chip and a MEMS chip attached to a substrate. These chips are generally enclosed by a conductive cover or lid. An acoustic input can be provided from an opening on a top surface of the microphone or from an opening on the substrate. Typically, in commercial applications where the acoustic input is from the top, an acoustic back cavity is formed mainly by a volume under the MEMS chip and the substrate. By contrast, in commercial applications where the acoustic input is from the bottom, the acoustic cavity is typically formed by the volume enclosed by the substrate and the cover.
It is desirable to provide improvements to MEMS microphones which allow them to be more easily manufactured at a lower cost. The improvement to the MEMS microphone must be easily implemented, cost effective and adaptable to existing manufacturing processes.
The present invention addresses such a need.